*** tcp_output.c.~1.205.~	2018-04-18 06:10:31.000000000 +0300
--- tcp_output.c	2018-04-18 15:16:20.213923329 +0300
***************
*** 988,1003 ****
  		 * taking into account that we are limited by
  		 * TCP_MAXWIN << tp->rcv_scale.
  		 */
! 		long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
! 			(tp->rcv_adv - tp->rcv_nxt);
  
  		/*
! 		 * If the new window size ends up being the same as the old
! 		 * size when it is scaled, then don't force a window update.
  		 */
! 		if ((tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale ==
! 		    (adv + tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale)
  			goto dontupdate;
  		if (adv >= (long) (2 * rxsegsize))
  			goto send;
  		if (2 * adv >= (long) so->so_rcv.sb_hiwat)
--- 988,1014 ----
  		 * taking into account that we are limited by
  		 * TCP_MAXWIN << tp->rcv_scale.
  		 */
! 		long recwin = min(win, (long)TCP_MAXWIN << tp->rcv_scale);
! 		long oldwin, adv;
  
  		/*
! 		 * rcv_nxt may overtake rcv_adv when we accept a
! 		 * zero-window probe.
  		 */
! 		if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
! 			oldwin = tp->rcv_adv - tp->rcv_nxt;
! 		else
! 			oldwin = 0;
! 
! 		/*
! 		 * If the new window size ends up being the same as or
! 		 * less than the old size when it is scaled, then
! 		 * don't force a window update.
! 		 */
! 		if (recwin >> tp->rcv_scale <= oldwin >> tp->rcv_scale)
  			goto dontupdate;
+ 
+ 		adv = recwin - oldwin;
  		if (adv >= (long) (2 * rxsegsize))
  			goto send;
  		if (2 * adv >= (long) so->so_rcv.sb_hiwat)